Surveillance for detection of persons, vehicles and other equipment is often conducted using infrared detectors. Infrared detectors can identify the location of persons and equipment based on variations between the surface temperature of objects in an ambient environment and the temperature of the skin and clothing of the individuals or the surfaces of equipment. Infrared detectors can thereby detect individuals and equipment in conditions in which detection using visible light would be ineffective, such as night time and low light conditions, and despite camouflage that renders individuals and equipment difficult to detect using optical wavelengths.
By way of example, a swimmer may seek to approach a shoreline from a body of water, without detection. As the swimmer approaches the shoreline, the swimmer's head and shoulders are above the surface of the water for extended periods of time in which the thermal energy radiated from these areas of the body may be easily detected with thermal sensors and imagers.
During an exemplary infiltration mission, a swimmer may approach an onshore area by entering the water in an area of open ocean beyond the surf region of the shoreline. The swimmer may need to swim along the shoreline to arrive at an approach area. While swimming parallel to the shoreline, the swimmer is in open ocean or in the surf and may be performing observation of the shore area in addition to swimming toward an intended approach region of the beach. In open ocean, the majority of the swimmer's body is beneath the water's surface and is thereby protected from detection by thermal imagers. However, the shoulders and head are exposed for most of this time having a potentially significant temperature gradient relative to the surrounding ocean and may easily be detected by infrared detection devices, such as thermal imaging devices. This facilitates detection of swimmers using thermal imaging devices, either from detection points on shore or from other vessels. A solution for addressing the foregoing challenges is desired.